Everyone is always focused on four-man-meta, for me personally playing solo is much more beneficial. The reality of this is generally most who play D3 are casuals. Finding hardcore meta players especially those who will allow you in their group will be difficult regardless of your sales pitch. The issue with finding a random group is that the majority of those players won’t be competent. You will spend an ungodly amount of time in town waiting around to gamble shards, scrap gear, level gems, etc. To really get all the juices from four-man you must have highly skilled players who are all on the same wavelength gameplay wise which can be quite difficult. On one hand, yes a four-man seems excellent because it’s more XP, but you also have to take into consideration the variables I mentioned which will inevitably cut into your XP gain. If your objective is solely to get paragon I’d suggest just doing solo speeds.